The only way to justify 13...Nbd7. Black is right in time to save the bishop. The idea is to play …g6-g5 and bring it back.
12. h1g1 It's important to keep the pawn on g4 in order to restrict the c2-bishop. 12... h5g4  13. h3g4  13... b8d7 Ding finds a strong novelty, although it took him a long time on the clock. 14. f3d2 The bishop is stuck on c2, but Ding had foreseen this.